1. Field of the Invention
The present invention relates to an inflator in which a flow amount of a pressurized gas can be kept stable at a time of activation, and a filter for an inflator suitable for the inflator.
2. Description of the Related Art
In a conventional inflator for an air bag utilizing a pressurized gas, as shown in FIG. 1, a filter 20 is disposed in front of a gas discharging port 18 to prevent fragments of a first rupturable plate 22 or the like from entering an air bag. As the filter 20, a wire mesh or a porous flat plate is used.
In the inflator shown in FIG. 1, however, the filter 20 is formed flat, and, when the first rupturable plate 22 is ruptured into small fragments at activation, plural fragments close holes in the filter 20, blocking flow of the pressurized gas. As a result, even if inflators having the same specification are used, there occur variations in activation performance among the inflators as shown in FIG. 6. FIG. 6 shows pressure changes in a tank in a 60-liter tank test, in which there is variations in pressure change with time. The details of a test method shown in FIG. 6 are similar to examples. Thus, when variations among inflators occur in pressure change at the time of activating the inflators, variations occur among inflated states of air bags, which has to be improved in view of a passenger protection.
As related art JP-B No. 3001985 and JP-A 2000-508985 are known.
In JP-B No. 3001985, an opening portion of a container including a pressurized medium is closed by a burst disc, and a filter is disposed in front of the burst disc. The filter prevents fragments of the burst disc from entering a valve assembly.
In JP-A 2000-508985, a top member formed with an outlet is attached to an end portion of a pressure container containing a pressurized medium and a disk is further when variations among inflators occur in pressure change at the time of activating the inflators, variations occur among inflated states of air bags, which has to be improved in view of a passenger protection.
As related arts, JP-B No. 3001985 and JP-A 2000-508985 are known.
In the invention described in JP-B No. 3001985, an opening portion of a container including a pressurized medium 50 is closed by a burst disc 48, and a filter 108 is disposed in front of the burst disc. The filter 108 prevents fragments of the burst disc 108 from entering a valve assembly 40. In the invention described in JP-A 2000-508985, a top member 30 formed with an outlet 40 is attached to an end portion of a pressure container 22 containing a pressurized medium and a disk 34 is further arranged. A perforated screen, a filter or a trap 42 is disposed between the outlet 40 and the disk 34. The screen 42 arrests particles contained in a discharged gas flow.